1. Technical Field of the Invention
The present invention relates to an integrated electronic circuit comprising at least one capacitor, and more particularly to an integrated circuit in which the operation of a capacitor is liable to be disturbed by semiconductor components placed in proximity to the capacitor, or vice versa.
2. Description of Related Art
Electronic circuits intended for many applications comprise first capacitors having essentially planar metal plates, in addition to other semiconductor components, such as transistors, diodes and resistors, or, possibly, second capacitors of a type different from the first capacitors. The essentially planar metal plates that constitute said first capacitors are substantially parallel to the surface of the substrate and may have relatively large geometrical dimensions such as, for example, sides of approximately 50 microns. Hereafter, “capacitors” denotes said first capacitors having essentially planar metal plates, it being understood that second capacitors, such as those introduced above, may be present among said semiconductor components.
These capacitors may be placed on the surface of the substrate, alongside the semiconductor components. The expression “arrangement of the capacitors alongside the semiconductor components” is understood to mean a configuration in which a first part of the surface of the substrate supports the semiconductor components and a second part of the same surface of the substrate, separate from the first part, supports the capacitors. The area of the substrate occupied by the circuit is therefore large. The cost of the electronic circuit is therefore high.
Another possible configuration consists in placing the capacitors above the semiconductor components produced on the surface of the substrate within the layers of insulating material which cover the surface of the substrate and the semiconductor components. The expression “arrangement of the capacitors above the semiconductor components” is understood to mean a configuration in which the capacitors are superposed on the semiconductor components on top of the surface of the substrate which supports them. A major saving in substrate area results from this configuration compared with the previous configuration, thereby allowing, a consequent reduction in the cost of the corresponding electronic circuits.
Moreover, it is known that capacitors having dimensions like those mentioned above are particularly sensitive to electrical and/or electromagnetic interference. This is especially the case in electronic circuits referred to as “analog” circuits. The term “analog circuits” is understood to mean electronic circuits which operate with signals corresponding to frequencies of less than about 10 megahertz. Such circuits are found for example in mobile communication terminals. These are especially power management units or analog signal-processing circuits, such as filters, amplifiers, regulators, comparators, and the like. When the capacitors are placed above semiconductor components, the latter generate interference which disturbs the operation of the capacitors. Conversely, the capacitors may also disturb the operation of the components above which they are placed. Such interference is connected with the short distances that separate the capacitors from the semiconductor components when they are superposed with the latter.
There is a need for the superposition of capacitors and semiconductor components on top of a surface of a substrate in a manner which prevents reciprocal interference of the respective operations of the capacitors and semiconductor components.